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We study the personal credit market using unique individual-level data covering fintech and traditional lenders. We show that fintech lenders acquire market share by lending first to higher-risk borrowers and then to safer borrowers, and rely mainly on hard information to make credit decisions. Fintech borrowers are significantly more likely to default than neighbor individuals with the same characteristics borrowing from traditional financial institutions. Furthermore, they tend to experience a short-lived reduction in the cost of credit, because their indebtedness increases more than non-fintech borrowers after loan origination. However, fintech lenders’ pricing strategies are likely to take this into account.

This lecture focuses on the costs of public debt when safe interest rates are low. I develop four main arguments. First, I show that the current US situation, in which safe interest rates are expected to remain below growth rates for a long time, is more the historical norm than the exception. If the future is like the past, this implies that debt rollovers, that is the issuance of debt without a later increase in taxes, may well be feasible. Put bluntly, public debt may have no fiscal cost. Second, even in the absence of fiscal costs, public debt reduces capital accumulation, and may therefore have welfare costs. I show that welfare costs may be smaller than typically assumed. The reason is that the safe rate is the risk-adjusted rate of return to capital. If it is lower than the growth rate, it indicates that the risk-adjusted rate of return to capital is in fact low. The average risky rate however also plays a role. I show how both the average risky rate and the average safe rate determine welfare outcomes. Third, I look at the evidence on the average risky rate, i.e., the average marginal product of capital. While the measured rate of earnings has been and is still quite high, the evidence from asset markets suggests that the marginal product of capital may be lower, with the difference reflecting either mismeasurement of capital or rents. This matters for debt: the lower the marginal product, the lower the welfare cost of debt. Fourth, I discuss a number of arguments against high public debt, and in particular the existence of multiple equilibria where investors believe debt to be risky and, by requiring a risk premium, increase the fiscal burden and make debt effectively more risky. This is a very relevant argument, but it does not have straightforward implications for the appropriate level of debt. My purpose in the lecture is not to argue for more public debt, especially in the current political environment. It is to have a richer discussion of the costs of debt and of fiscal policy than is currently the case.

In recent years, central banks have increasingly turned to forward guidance as a central tool of monetary policy. Standard monetary models imply that far future forward guidance has huge effects on current outcomes, and these effects grow with the horizon of the forward guidance. We present a model in which the power of forward guidance is highly sensitive to the assumption of complete markets. When agents face uninsurable income risk and borrowing constraints, a precautionary savings effect tempers their responses to changes in future interest rates. As a consequence, forward guidance has substantially less power to stimulate the economy.

We revisit the transmission mechanism from monetary policy to household consumption in a Heterogeneous Agent New Keynesian (HANK) model. The model yields empirically realistic distributions of wealth and marginal propensities to consume because of two features: uninsurable income shocks and multiple assets with different degrees of liquidity and different returns. In this environment, the indirect effects of an unexpected cut in interest rates, which operate through a general equilibrium increase in labor demand, far outweigh direct effects such as intertemporal substitution. This finding is in stark contrast to small- and medium-scale Representative Agent New Keynesian (RANK) economies, where the substitution channel drives virtually all of the transmission from interest rates to consumption. Failure of Ricardian equivalence implies that, in HANK models, the fiscal reaction to the monetary expansion is a key determinant of the overall size of the macroeconomic response.

We document the transmission of large-scale asset purchases by the Federal Reserve to the real economy using rich borrower-linked mortgage-market data and an identification strategy based on mortgage market segmentation. We find that central bank QE1 MBS purchases substantially increased refinancing activity, reduced interest payments for refinancing households, led to a boom in equity extraction, and increased aggregate consumption. Relative to QE-ineligible jumbo mortgages, QE-eligible conforming mortgage interest rates fell by an additional 40 bp and refinancing volumes increased by an additional 56% during QE1. We estimate that households refinancing during QE1 increased their durable consumption by 12%. Our results highlight that the transmission of unconventional monetary policy to the real economy depends crucially on the composition of assets purchased and the degree of segmentation in the market.

We present evidence of a risk-taking channel of monetary policy for the U.S. banking system. We use confidential data on banks' internal ratings on loans to businesses over the period 1997 to 2011 from the Federal Reserve's Survey of Terms of Business Lending. We find that ex ante risk-taking by banks (measured by the risk rating of new loans) is negatively associated with increases in short-term interest rates. This relationship is more pronounced in regions that are less in sync with the nationwide business cycle, and less pronounced for banks with relatively low capital or during periods of financial distress.

The uncovered interest parity puzzle concerns the empirical regularity that high interest rate countries tend to have high expected returns on short term deposits. A separate puzzle is that high real interest rate countries tend to have currencies that are stronger than can be accounted for by the path of expected real interest differentials under uncovered interest parity. These two findings have apparently contradictory implications for the relationship of the foreign-exchange risk premium and interest-rate differentials. We document these puzzles, and show that existing models appear unable to account for both. A model that might reconcile the findings is discussed.

We investigate the association between financial constraints and cash savings generated through tax planning. We predict that an increase in financial constraints leads firms to increase internally generated funds via tax planning. We measure financial constraints based on changes in firm-specific and macroeconomic measures. We find that firms facing increases in financial constraints exhibit increases in cash tax planning. Our results indicate that among profitable firms, firm-years with the largest increases in firm-specific constraints are associated with declines in firms' cash effective tax rates ranging from 3.00 to 5.14 percent, which equate to between 2.87 and 4.82 percent of operating cash flows. We also find that (1) the impact of financial constraints on tax planning is greatest among firms with low cash reserves, and (2) constrained firms achieve a substantial portion of their current tax savings via deferral-based tax planning strategies, despite the lack of a financial statement benefit.

We examine net arbitrage trading (NAT) measured by the difference between quarterly abnormal hedge fund holdings and abnormal short interest. NAT strongly predicts stock returns in the cross-section. Across ten well-known stock anomalies, abnormal returns are realized only among stocks experiencing large NAT. Exploiting Regulation SHO, which facilitated short selling for a random group of stocks, we present causal evidence that NAT has stronger return predictability among stocks facing greater limits to arbitrage. We also find large returns for anomalies that arbitrageurs chose to exploit despite capital constraints during the 2007–09 financial crisis. We confirm our findings using daily data.

Using a novel source of quasi-experimental variation in interest rates, we develop a new approach to estimating the Elasticity of Intertemporal Substitution (EIS). In the U.K., the mortgage interest rate features discrete jumps—notches—at thresholds for the loan-to-value (LTV) ratio. These notches generate large bunching below the critical LTV thresholds and missing mass above them. We develop a dynamic model that links these empirical moments to the underlying structural EIS. The average EIS is small, around 0.1, and quite homogeneous in the population. This finding is robust to structural assumptions and can allow for uncertainty, a wide range of risk preferences, portfolio reallocation, liquidity constraints, present bias, and optimization frictions. Our findings have implications for the numerous calibration studies that rely on larger values of the EIS.